The crankshaft is the heart of the engine, and the quality of the crankshaft directly affects the quality of the automobile. The crankshaft journal of car engine crankshaft usually adopts medium frequency induction hardening process. FAW Group mainly uses rotary quenching technology on the heat treatment of crankshaft surface to perform surface treatment on the main journal, connecting rod neck, flange and thrust surface. More than ten years of history. With the advancement of science and technology, people's requirements for heat treatment of crankshafts are becoming higher and higher. Now, most well-known automobile and diesel engine manufacturers have begun to strengthen the corners of the crankshaft, which can greatly improve the service life of the crankshaft and the whole car. Machine quality.

According to the traditional production operation method, the crankshaft is not quenched with rounded corners, but the failure mode of the crankshaft is just to break from the rounded corners, which is the weakest part and the part where the crankshaft is subjected to the most stress. The forces encountered when the crankshaft is working are quite complex. The stress conditions of the main journal, connecting rod journal and crank arm are different, but they are mainly subjected to repeated bending and torsional loads, while the main journal and connecting rod journals are also subject to strong friction. . The damage form of the crankshaft is mainly the fracture caused by fatigue and the wear of the journal, so improving the fatigue strength of the crankshaft is the first task before us.

Crankshaft fractures are mostly fatigue fractures, and the fatigue source is located at the bottom dead center R of the connecting rod neck where the crankshaft is subjected to the most stress. Therefore, after induction hardening, the crankshaft journal can increase the hardness of the journal and increase its wear resistance. After the neck fillet is quenched, the fatigue strength of the crankshaft is greatly improved, and the possibility of fatigue fracture is greatly reduced. In addition, the stress relief annealing of the crankshaft blank effectively eliminates the stress generated during the forging process, which reduces the post-cold working stress, releases the stress before quenching, and greatly reduces the amount of deformation after quenching.

There are two ways to improve the fatigue strength of the crankshaft: one is to choose different materials, such as replacing 45 steel with alloy materials; the other is to use different processes, such as induction hardening of the 45 steel crankshaft with rounded corners, and the rounding of the crankshaft. Nitriding the crankshaft as a whole. The test proves that the rounded induction hardened crankshaft has the highest fatigue strength (996MPa), the rounded rolled crankshaft fatigue strength is second (890MPa), and the nitrided crankshaft is third (720MPa). The method of round corner rolling is adopted, and the investment in supporting equipment is relatively large, requiring more than 20 million yuan; the method of nitriding is low and the company has no production equipment and capacity; Method, only need to increase the sensor and process, the least investment, the fastest effect, is the most economical and effective method to improve the fatigue strength of the crankshaft. The following describes a quenching process of crankshaft journal fillet.